The present invention relates to an optical head for focusing light beams for information reproduction and recording or information reproducing, recording and erasing to form a beam spot on an information recording medium. More particularly, this relates to an optical head for recording, reproducing or erasing information from the optical disk by using a plurality of light beams.
Different optical heads for recording/reproducing information using the medium of an optical disk have been recently developed and are commercially available. To record information, a region on a recording surface is irradiated with a beam spot of an intensity-modulated light beam formed by an objective lens, and this beam continuously changes the characteristic of the disk while the optical disk is continuously rotated. Apertures called pits are formed in the disk, or optical characteristics such as a refractive index and a reflectance are changed in order to record information in the recording surface of the optical disk. To reproduce information, a reproduction laser beam is focused by the objective lens to form a beam spot on the recording region, and the reproduction light beam is intensity-modulated by the state of the recording area. The reproduction beam is converted by a photodetector to an electrical signal.
A conventional optical head is already known wherein information is recorded in the optical disk while simultaneously confirming whether or not information is being properly recorded in the optical disk. Thus, the reproduction light beam is focused on the optical disk even in the recording mode. In addition, another conventional optical head is known wherein a tracking guide is provided to specify an information recording area. In the optical head having the tracking guide wherein information is recorded while confirming whether or not information is properly recorded in the optical disk, the light beam must always trace the tracking guide. For this purpose, a tracking guide detection system is arranged in the optical head. However, in the recording mode, since the recording/reproduction light beam is reflected from the optical disk, the tracking guide cannot be stably detected, resulting in inconvenience.
In the optical head for recording, reproducing and erasing information, detection of the tracking guide may be affected by an erasing light beam during an erasing mode.